Stanislaus County Sheriff Adam Christianson said that Arriaga had crossed the border into Arizona illegally several years ago and was planning to flee to Mexico after the shooting.

Arriaga had two previous arrests for DUIs, and Singh stopped him for a suspected DUI.

Christianson argued that government policies had protected an undocumented immigrant with a criminal history. "So while we absolutely need to stay focused on Officer Singh's service and sacrifice, we can't ignore the fact that this could have been preventable," he said.

Arriaga claims he's a member of the Sureños, a Mexican American street gang from Southern California.

"All you have to do is take a look at social media, which by the way got way ahead of us again, and there's plenty of photographic evidence on and in social media, Facebook and other platforms, that clearly shows himself promoting himself as a gangster," said Christianson.

On Thursday, the sheriff's office confirmed that photos posted on social media of a man doing gang signs was the suspect they were looking for. Arriaga will be charged with homicide.

The following pictures of the suspect including a name &amp; birth date have been circulating on social media. We can confirm these are pictures of the man who murdered Corporal Ronil Singh. We CANNOT, however, confirm that the correct name or birth date is being put out.